By ERIC SCHMITT and CAROLYN MARSHALL

Published: March 19, 2006

CORRECTION APPENDED

As the Iraqi insurgency intensified in early 2004, an elite Special Operations forces unit converted one of Saddam Hussein's former military bases near Baghdad into a top-secret detention center. There, American soldiers made one of the former Iraqi government's torture chambers into their own interrogation cell. They named it the Black Room.

In the windowless, jet-black garage-size room, some soldiers beat prisoners with rifle butts, yelled and spit in their faces and, in a nearby area, used detainees for target practice in a game of jailer paintball. Their intention was to extract information to help hunt down Iraq's most-wanted terrorist, Abu Musab al-Zarqawi, according to Defense Department personnel who served with the unit or were briefed on its operations.

The Black Room was part of a temporary detention site at Camp Nama, the secret headquarters of a shadowy military unit known as Task Force 6-26. Located at Baghdad International Airport, the camp was the first stop for many insurgents on their way to the Abu Ghraib prison a few miles away.

Placards posted by soldiers at the detention area advised, ''NO BLOOD, NO FOUL.'' The slogan, as one Defense Department official explained, reflected an adage adopted by Task Force 6-26: ''If you don't make them bleed, they can't prosecute for it.'' According to Pentagon specialists who worked with the unit, prisoners at Camp Nama often disappeared into a detention black hole, barred from access to lawyers or relatives, and confined for weeks without charges. ''The reality is, there were no rules there,'' another Pentagon official said.

The story of detainee abuse in Iraq is a familiar one. But the following account of Task Force 6-26, based on documents and interviews with more than a dozen people, offers the first detailed description of how the military's most highly trained counterterrorism unit committed serious abuses.

It adds to the picture of harsh interrogation practices at American military prisons in Afghanistan and Guant?mo Bay, Cuba, as well as at secret Central Intelligence Agency detention centers around the world.

The new account reveals the extent to which the unit members mistreated prisoners months before and after the photographs of abuse from Abu Ghraib were made public in April 2004, and it helps belie the original Pentagon assertions that abuse was confined to a small number of rogue reservists at Abu Ghraib.

The abuses at Camp Nama continued despite warnings beginning in August 2003 from an Army investigator and American intelligence and law enforcement officials in Iraq. The C.I.A. was concerned enough to bar its personnel from Camp Nama that August.

It is difficult to compare the conditions at the camp with those at Abu Ghraib because so little is known about the secret compound, which was off limits even to the Red Cross. The abuses appeared to have been unsanctioned, but some of them seemed to have been well known throughout the camp.

For an elite unit with roughly 1,000 people at any given time, Task Force 6-26 seems to have had a large number of troops punished for detainee abuse. Since 2003, 34 task force members have been disciplined in some form for mistreating prisoners, and at least 11 members have been removed from the unit, according to new figures the Special Operations Command provided in response to questions from The New York Times. Five Army Rangers in the unit were convicted three months ago for kicking and punching three detainees in September 2005.

Some of the serious accusations against Task Force 6-26 have been reported over the past 16 months by news organizations including NBC, The Washington Post and The Times. Many details emerged in hundreds of pages of documents released under a Freedom of Information Act request by the American Civil Liberties Union. But taken together for the first time, the declassified documents and interviews with more than a dozen military and civilian Defense Department and other federal personnel provide the most detailed portrait yet of the secret camp and the inner workings of the clandestine unit.

The documents and interviews also reflect a culture clash between the free-wheeling military commandos and the more cautious Pentagon civilians working with them that escalated to a tense confrontation. At one point, one of Defense Secretary Donald H. Rumsfeld's top aides, Stephen A. Cambone, ordered a subordinate to ''get to the bottom'' of any misconduct.

Most of the people interviewed for this article were midlevel civilian and military Defense Department personnel who worked with Task Force 6-26 and said they witnessed abuses, or who were briefed on its operations over the past three years.

Many were initially reluctant to discuss Task Force 6-26 because its missions are classified. But when pressed repeatedly by reporters who contacted them, they agreed to speak about their experiences and observations out of what they said was anger and disgust over the unit's treatment of detainees and the failure of task force commanders to punish misconduct more aggressively. The critics said the harsh interrogations yielded little information to help capture insurgents or save American lives.

Correction: March 22, 2006, Wednesday
A front-page article on Sunday about detainee abuse by a Special Operations unit in Iraq, Task Force 6-26, misstated the given name of the Defense Intelligence Agency's former director for human intelligence, who said he had not heard reports of abuse until he was briefed in June 2004. He is Maj. Gen. Michael E. Ennis, not George.